I live in Westminster and starting every August I hear three distinct night-time insects: cicadas (infrequently), katydids (constantly), and an unidentified bug that emits short (3-4 seconds) bursts of clicks.  These occur about every 60 seconds or so, are usually higher in the trees, and appear to be calling/answering others about 100' away or so.

What in the heck are these guys?  I can't get close enough to see them so I have no description for you.

Thank you!

Charles